What Is E. Coli?

Some strains of E. coli are essential to good health — but others can cause severe illness.

Escherichia coli, or E. coli, is a type of bacteria commonly found in the intestines of warm-blooded animals, including humans.

The vast majority of E. coli strains are harmless, or even beneficial.

For instance, E. coli produces vitamins K and B6, and maintains a protective space in your gut for other beneficial bacteria.

However, some strains of E. coli can cause sickness and severe complications.

E. Coli Infections

If the bacteria enter your urinary tract, they can cause a urinary tract infection (UTI) — in fact, E. coli is behind more than 85 percent of all UTIs, according to a 2012 report in the journal Emerging Infectious Diseases.

When E. coli finds its way into the lungs, it can cause respiratory illness and, in rare cases, pneumonia.

According to the Meningitis Research Foundation, E. coli is the cause of about 20 percent of all cases of neonatal meningitis, a potentially deadly infection of the membranes lining an infant's brain and spinal cord.

But E. coli is perhaps best known for its role in intestinal infections and outbreaks of food poisoning.

But you can also get food poisoning from Escherichia coli, or E. coli.

A type of E. coli called Shiga toxin-producing E. coli, or STEC, causes about 176,000 cases of foodborne illnesses each year — approximately 36 percent of these cases are due to a specific strain called O157:H7 (or O157), according to a 2011 article in the CDC-published journal Emerging Infectious Diseases.

Additionally, O157 is responsible for about 4 percent of all food poisoning hospitalizations by pathogenic microorganisms, the study found.

Cattle are the most common reservoirs for E. coli, which can get into people when they eat food that's contaminated with the animals' bacteria-carrying feces.

Typical sources of contamination include:

Ground beef

Unpasteurized dairy products and juices, including apple juice

Produce exposed to water runoff from cattle farms

Well water or open water (lakes, rivers) frequented by animals

People can also pass E. coli to you if they touch your food or you (and you don't wash your hands before eating).

Additionally, you may get E. coli in your system if you ingest water while swimming in a contaminated lake, river, or swimming pool.

You'll start to experience the effects of an E. coli intestinal infection 2 to 5 days after the bacteria get into your system.

Less-common symptoms include vomiting and low-grade fever. Most healthy adults recover from an STEC infection completely after about a week without any medical attention.

E. Coli Infections in Children

As is the case with adults, pathogenic E. coli in children most commonly causes food poisoning and urinary tract infections (UTIs).

UTIs affect about 3 percent of all children in the United States and result in more than 1 million pediatrician visits each year, according to National Institutes of Health (NIH).

Because of their anatomy, girls are four times more likely to get a UTI than boys.

Uncircumcised boys younger than 6 months old are also more likely to get a UTI than circumcised boys of the same age, according to the NIH.

Escherichia coli is also responsible for about 20 percent of neonatal meningitis (an infection of the membranes surrounding an infant's brain and spinal cord), according to the Meningitis Research Foundation.

Toddlers can pass the bacteria to their playmates (especially if they're not potty trained), and adults can pass it to other children if they don't wash their hands after changing a child's diapers, according to the Centers for Disease Control and Prevention (CDC).

What's more, children can still spread E. coli to other people for 2 weeks after they've gotten over their sickness, the CDC reports.

E. Coli and Hemolytic Uremic Syndrome (HUS)

About 5 to 15 percent of STEC infections lead to a life-threatening condition called hemolytic uremic syndrome (HUS), in which the bacteria's toxins destroy red blood cells.

Young children, the elderly, and people with weakened immune systems are more likely to experience severe STEC symptoms or get HUS, according to a 2012 report in the journal Toxins.

Complications from E. Coli Intestinal Infections

With rest and lots of water, most healthy adults recover from an E. coli infection within a week.

But if you don't replenish the fluid you lose from diarrhea and vomiting, you could become dehydrated. Initially, dehydration only causes mild symptoms, such as headaches, fatigue, and muscle aches.

However, severe dehydration can result in more serious health issues, including dizziness, delirium, rapid heartbeat, and cardiac and kidney problems.

It can potentially cause seizures, permanent brain damage, and death.

Complications from UTIs

Doctors treat UTIs with antibiotics. However, complications can arise if the infection isn't detected early, or if the antibiotics don't work (some types of E. coli are resistant to most currently available antibiotics).

If the bacteria spread throughout the urinary system, they can cause kidney infections.

These infections can result in permanent kidney damage, which often lead to kidney scars, decreased kidney function, and high blood pressure.

A kidney infection, if severe enough, could also cause kidney failure.

In the most severe cases, UTIs can lead to a blood infection called sepsis, or septicemia, which can cause the blood pressure to drop.

With poor blood flow, major organs and body systems will stop working properly — and without treatment, the disease can ultimately cause death.

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